Guidance on Reducing the Risk of Salmonella Enteritidis in Canadian Shell Eggs

Transcription

1 Guidance on Reducing the Risk of Salmonella Enteritidis in Canadian Shell Eggs August 2012 Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 1

2 TABLE OF CONTENTS 1. Scope Definitions Roles and Responsibilities Government Industry Consumers Introduction Background Consultation Risk Assessment Overview Guidance to Improve the Microbiological Quality of Shell Eggs Guidance for the Production of Table Eggs Primary Breeders and Egg-Type Multiplier Breeders Production of day-old chicks Pullet rearing S. Enteritidis testing in pullet and laying flocks Actions to be taken upon finding S. Enteritidis-positive flocks On-Farm Food Safety program recommendations Vaccination programs Guidance when Eggs are Implicated in Human Illness Post-Production Guidance for Table Eggs Imported shell eggs destined for the table market Surplus hatching eggs Table eggs from unregulated and small producers Sale of ungraded shell eggs Sale of cracked eggs Refrigeration of shell eggs Egg-grading stations Processed egg stations Education campaigns Implementation References Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 2

3 1. Scope This document is intended to provide guidance to reduce the risk of foodborne illness due to Salmonella enterica subspecies enterica serovar Enteritidis (hereafter referred to as S. Enteritidis) in shell eggs. The document provides guidance on intervention strategies to reduce the risk of S. Enteritidis in shell eggs produced by domestic hens (Gallus gallus) offered for sale on the table market in Canada. It was developed using a health risk assessment approach (DeWinter et al., 2011). Known limitations in the ability to identify S. Enteritidis in eggs have resulted in controls aimed at reducing S. Enteritidis being put in place at the level of the laying flock. When S. Enteritidis is identified in the environment of a laying flock, the eggs from that flock are sent to pasteurization for the lifetime of the flock. Therefore, this document provides guidance regarding best practices for the egg industry, provincial/territorial and federal governments, primary breeders and egg-type multiplier flocks, and portions of the pullet, hatchery and broiler industries that can affect the presence of S. Enteritidis in the egg industry. International evidence also demonstrates that any control plan for S. Enteritidis in poultry must use a top-down approach, that is, one for which the controls begin at the breeding stock that supply all of the hens for the egg industry. For this reason, the guidance document also covers the primary breeding stock, the hatchery supply flocks, as well as the hatcheries. The information contained in this document is based on the current state of scientific evidence and developments are ongoing. This guidance document represents a consensus-based standard that should be implemented in the industry on a voluntary basis with the possibility of regulatory backstops in the future, if warranted. Food safety enforcement bodies at the federal, provincial and territorial level may use this guidance document as a reference to assess adherence of the egg industry to good agricultural practices as they relate to the reduction of S. Enteritidis in shell eggs. Thus, this guidance may be used to assess compliance with general requirements of food safety legislation or regulations, in particular, compliance with Sections 4 and 7 of the Food and Drugs Act. 2. Definitions For the purpose of this document the following definitions apply. 2.1 Broiler flock. A flock of domestic chickens selectively bred and reared for their meat. 2.2 Cracked egg. An egg with a damaged shell, but with an intact membrane, such that the egg contents are not leaking. 2.3 Farm gate. The premises of the egg producer where the laying flock resides. 2.4 Flock. A flock comprises domestic chickens housed in an individual barn. 2.5 Flock testing. The environmental testing of an egg-type pullet or laying flock to determine whether the flock is infected with S. Enteritidis. 2.6 Laying flock. A flock of domestic hens during the production of eggs for human consumption. 2.7 Nest Run egg. A Canada Grade designation under the Canadian Egg Regulations. Nest Run eggs are to be sent to a registered processed egg station. Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 3

4 2.8 Pullet flock. A flock of domestic hens prior to the period of production of eggs for human consumption or for hatching. 2.9 Regulated flock. Laying flocks that are regulated by the provincial egg board and that operate under the national supply management system Shell egg. A whole, intact egg laid by a domestic hen Table egg. A shell egg offered for sale to consumers (including retail environments, restaurants, bakeries, and other foodservice and institutional settings) for the purposes of consumption Test and divert flock management strategy. Management of a laying flock such that it is tested for S. Enteritidis, and if found positive, all eggs are diverted to pasteurization for the lifetime of the flock Ungraded egg. Ungraded eggs comprise shell eggs that have not been graded at a federally registered egg station Unregulated flock. Unregulated flocks are those with fewer birds than the limits set by the provincial egg marketing boards. These limits vary by province and can range from 99 to 499 birds. 3. Roles and Responsibilities This guidance document, developed as a joint effort between Health Canada, the Canadian Food Inspection Agency (CFIA) and the Public Health Agency of Canada (PHAC), takes into account the roles and responsibilities of industry, government and consumers. 3.1 Government Health Canada has a responsibility for developing and setting food safety standards that identify the nature and assess the level of risk associated with the consumption of contaminated food products and develops guidance documents to help minimize the risk of foodborne illnesses. Health Canada consults and works with the CFIA and provincial/territorial governments on the above to ensure that public health responses are appropriate and effective. It is the role of the CFIA and provincial/territorial governments to oversee the food industry to ensure that it meets its food safety responsibilities including the application of effective and timely management strategies appropriate to the risk, when required. The role of PHAC is to promote and protect the health of Canadians through leadership, partnership, innovation and action in public health. PHAC has already begun to play a more active role in food surveillance across the country, e.g., C-EnterNet, a multi-partner program designed to detect changes in trends in human enteric disease and in levels of pathogen exposure from food, animal and water sources in Canada. In addition, the three federal departments provide reference laboratory services, conduct food safety investigations, Health Risk Assessment (HRA) and recall actions. 3.2 Industry It is industry's role and responsibility to comply with all applicable legislative and regulatory requirements which include Sections 4 and 7 of the Food and Drugs Act and to develop and implement good manufacturing practices and controls that are conducive to the production of safe eggs. Food distributors and retailers are responsible for controlling the temperature of shell eggs during transport and storage to suppress or limit bacterial growth. Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 4

5 3.3 Consumers In addition to government agencies and food industries working diligently at minimizing the exposure to S. Enteritidis, consumers also have an important role to play in the farm-to-fork continuum in adopting safe egg handling and preparation practices. Caterers, parents of young children and care providers for the elderly and other vulnerable populations have a higher level of responsibility in this regard. To this end, Health Canada, the CFIA and the PHAC (and other provincial/territorial bodies) develop and deliver science-based educational material to inform consumers and health care providers about the hazards associated with S. Enteritidis in shell eggs and how to minimize the risks of foodborne disease, with a particular focus on vulnerable populations and their families, as well as their care providers. 4. Introduction Salmonella is an important foodborne pathogen worldwide. Ingestion of the organism is followed by an incubation period, usually eight to 72 hours, during which the organism proliferates in the gut. Symptoms of salmonellosis range from mild to severe diarrhea, abdominal pain and vomiting, as well as fever accompanied by headache and chills. In cases of severe diarrhea, dehydration may lead to hypotension, cramps, oliguria and uraemia. The vast majority of cases comprise acute illness that lasts a few days, with recovery occurring within a week. Death is uncommon except in the very young, very old, or immunocompromised individuals. Small proportions of cases develop bacteraemia or meningitis, or may develop localised infections causing abscesses, arthritis, cholecystitis, endocarditis, pericarditis or pneumonia. Long-term sequelae resulting from salmonellosis can include malabsorption of essential nutrients (which can result in a compromised immune system and may lead to infection), allergy, reactive arthritis, autoimmune disorders and neoplasia. Although reactive arthritis is usually of short duration, some patients may develop chronic disease and patients with certain underlying conditions (for example, haemoglobin abnormalities) may be prone to complications. Most serotypes of Salmonella contaminate shell eggs on the exterior shell surface, which is referred to as horizontal transmission. The organisms may gain entry to the interior contents by cracks in the shell or by other circumstances that can lead to eggshell penetration (for example, time and temperature abuse, improper egg washing). Scientifically designed and tested egg washing protocols used at egg grading stations must comply with Section 9 of the Egg Regulations of the Canada Agricultural Products Act. Egg washing serves to reduce the microbial load associated with egg shell surfaces, thereby reducing risk to consumers. Since the early 1990s, eggs have been established as a major vehicle for human cases of S. Enteritidis infections in the international scientific literature. S. Enteritidis is the key microbial pathogen in shell eggs because of trans-ovarian deposition, in other words, vertical transmission of the organisms into egg contents as a result of the infected reproductive tissues of laying hens. Laying hens may be infected with S. Enteritidis without showing any signs of illness or disease. The problem is exacerbated when contaminated shell eggs are not held under conditions of refrigeration, allowing the organisms to access the nutrient rich yolk and grow rapidly, and by consumers known preferences for eating raw and lightly-cooked eggs. There has been an increase in reports of S. Enteritidis outbreaks associated with other vehicles such as almonds and sprouted seeds. Reports of S. Enteritidis outbreaks associated with eggs Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 5

6 may have decreased due to the fact that eggs are an established vehicle of S. Enteritidis. However, eggs will remain an important vehicle of infection due to trans-ovarian transmission into intact eggs. This was demonstrated by the major 2010 U.S. outbreak of S. Enteritidis due to shell eggs with 1,939 known associated illnesses and in which over 500 million shell eggs were recalled (CDC, 2010). In Canada, Salmonella has been the second most common enteric bacterial pathogen since at least 1997, judging by Salmonella isolates referred to the National Microbiology Laboratory (PHAC, 2004) and cases reported through the national notifiable disease program (PHAC, 2009). S. Enteritidis consistently ranks among the top three serovars associated with human illness in Canada since at least 1995, and the top five since at least 1983 (PHAC, 2005; Health Canada, 2003; Khakhria et al., 1997). Compared to other serovars, S. Enteritidis isolates have increased dramatically since 2003 and are now the most prevalent serotype, having represented 28% of all salmonellosis cases in 2005 and 23% in 2006 (PHAC, 2007ab). 5. Background S. Enteritidis was noted to be an increasing human health problem through the 1980s, primarily in Europe and the United States, and researchers noted that there might be an association with infections of the ovaries and oviducts in laying flocks (St. Louis et al., 1988; Cowden et al., 1989). Over the next decade, it was established that S. Enteritidis could be deposited in the internal contents of an intact shell egg. The Egg Farmers of Canada (EFC) responded in 1990 with the launch of its Safe from Salmonella program, which was the first formal program in Canada to introduce biosecurity measures to primary commercial food production (CEMA, 2002). EFC also cooperated in an Agriculture and Agri-Food Canada research project to sample and inspect laying flocks and eggs to determine the extent of the problem with S. Enteritidis in Canada (Poppe et al., 1991; Poppe et al., 1992). In 1996, Health Canada developed an interim policy on the issue and the egg industry began to divert eggs to further processing to inactivate the organisms, when S. Enteritidis was identified in the environment of a laying flock. In 1998, EFC s Safe from Salmonella program was modified to incorporate Hazard Analysis Critical Control Point (HACCP) principles and renamed Start Clean Stay Clean TM, and was also modified to include free-range, free-run and specialty flocks such as organic operations. This On-Farm Food Safety program completed technical reviews by the CFIA in 2004 and The program includes a number of practices intended to minimize the possibility of introducing Salmonella to a laying flock, as well as on farm inspections conducted by provincial and federal officers that provide each egg producer with a rating and suggestions for improvement. Among the regulated laying flocks that operate under the Canadian supply management system, EFC has been able to achieve over 90% participation in Start Clean Stay Clean TM, and 100% of egg producers are currently being tested for S. Enteritidis. Currently, the program is phasing in an insurance program (the Canadian Egg Industry Reciprocal Alliance) that may provide compensation when egg producers are faced with S. Enteritidis-infected flocks. Most of the table egg sector in Canada is regulated by the Egg Farmers of Canada and the egg marketing boards in the 10 provinces and the territories. Together they administer the production, pricing, marketing and promotion of eggs in Canada. Based upon egg production statistics for 2006 (Statistics Canada, 2007), eggs from regulated flocks account for approximately 97% of eggs on the table market. This estimate takes into account an estimate for table eggs from unregulated flocks based on Census of Agriculture data (Statistics Canada, 2007) Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 6

7 and EFC data for imported table eggs (CEMA, 2007). However, hatching eggs that proceed to the table market, sales at the farm gate, and sales at farmers markets are not accounted for in the estimate and therefore the estimate may be higher than the true value. The Canada Agricultural Products Act is the authority for the Egg Regulations, which specify certain requirements for eggs that relate to food safety. Eggs must be graded at federally-registered grading stations, which must meet requirements, including temperature and humidity controls for storage of eggs, and other hygienic requirements. During the grading process, cracked eggs only meet the grade Canada C, and thus are sent for pasteurization. Dirty eggs do not meet any Canada grade; they are considered unfit for human consumption. Grading stations are monitored regularly by the CFIA, and twice per year undergo environmental sampling for salmonellae. Positives are serotyped and corrective actions are required. Most of the provinces and territories refer to the Canadian Egg Regulations as the authority for table eggs in their jurisdiction. One noteworthy consideration is that grade A table eggs in Canada can originate from a number of sources, not just from regulated flocks. In general, there is very limited data about these other sources of eggs including their proportion of market share, flock management and egg storage and handling practices where they relate to the risk of S. Enteritidis, and the proportion of illnesses attributed to eggs from these sources. Therefore, although this guidance document mainly addresses recommendations for table eggs from regulated flocks, it also makes recommendations recognizing that the additional sources of eggs reaching the table market also represent a potential risk to consumers. The coverage of the On-Farm Food Safety programs (including environmental testing for S. Enteritidis), monitored and controlled egg storage and handling practices, carefully controlled egg washing practices, and governmental surveillance and monitoring programs in place to reduce the risk of S. Enteritidis in grade A table eggs, do not necessarily extend to eggs originating from other sources and therefore sources of table eggs outside of the regulated flocks may represent an increased risk to consumers. 6. Consultation This document has been prepared by experts from Health Canada, CFIA, and the Public Health Agency of Canada (PHAC). Input has been sought from key industry stakeholders including the Egg Farmers of Canada (EFC), the Canadian Hatching Egg Producers (CHEP), and the Canadian Poultry and Egg Processor s Council (CPEPC) during the development of this guidance document, and was given full consideration in the development of this guidance. Furthermore, Health Canada hosted a public consultation to gather opinions from the public, veterinary professionals, agriculture professionals, health professionals, people in the food industry, and others who might be affected by the guidance document. The input received from the consultation period was given full consideration and the guidance document underwent significant revision. A report from the public consultation will be posted on Health Canada's Web site and was also ed to all participants. 7. Risk Assessment Overview A risk assessment entitled Risk Assessment of Shell Eggs Internally Contaminated with Salmonella Enteritidis was published by Health Canada in 2011 (DeWinter et al., 2011). The development of the risk assessment involved an extensive literature review, as well as consultation with experts from the CFIA and PHAC. Interested parties are invited to consult the Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 7

8 risk assessment for additional details or information, as it contains an extensive review of many aspects related to S. Enteritidis that are not covered in this guidance document;. The risk assessment highlighted the fact that eggs are consumed by every segment of the Canadian population. Egg consumption in 2005 was 15.6 dozen per person per year (Agriculture and Agri-Food Canada, 2006). Since 1995, per capita processed egg consumption has increased by 30% (Agriculture and Agri-Food Canada, 2006). In 2005, the total production of eggs for human consumption in Canada was approximately 6.3 billion, of which approximately 75% were sold as table eggs (Agriculture and Agri-Food Canada, 2006). The remaining eggs are sent to processed egg stations to be pasteurized for use in processed egg products. Normal and susceptible populations consume an average of 74.7% and 79.0% of shell eggs, respectively, in a home setting, with the balance of consumption occurring in a food service and institutional (FSI) setting. In total, normal and susceptible populations consume an average of 0.14, 12.7, and 87.2% of raw, lightly cooked, and well-cooked egg meals in home settings, and 0.11, 13.7, and 86.2% in FSI settings. Susceptible populations consume an average of 0.25, 12.8, and 87.0% of raw, lightly cooked, and well cooked egg meals in home settings, and 0.04, 11.0, and 89.0% in FSI settings. Due to data limitations, the scope of the risk assessment comprised internally contaminated eggs produced by the regulated laying flocks participating in environmental testing for S. Enteritidis in the years 2005 and Therefore, the risks of illness from S. Enteritidis due to externally contaminated eggs, cracked eggs, dirty eggs, imported eggs, eggs from unregulated producers (farm gate, farmers markets), hatchery surplus eggs (layer- and broiler-breeders), and ungraded eggs were not included in the risk assessment. The results of the risk assessment demonstrated that an average of approximately 5 per 1000 regulated laying flocks were infected per year. The distribution of the prevalence of contaminated eggs yielded an average of 1.7 per million eggs from the regulated laying flocks. The results also demonstrated that consumers are 2.7 times more likely to become ill from consumption of eggs in a FSI setting than in a home setting. Susceptible individuals are 1.4 to 1.5 times more likely to become ill from consumption of a serving from a contaminated egg than normal individuals. Illnesses were found to be disproportionate to exposures, with the poorest storage and handling conditions representing only 0.6% of exposures but resulting in 46% of illnesses, whereas ideal storage and handling conditions accounted for 96% of exposures, but 49% of illnesses. These findings suggested that risk management options targeting both contaminated egg prevalence and the number of illnesses that result from an S. Enteritidiscontaminated egg would be appropriate. Simulations of risk management strategies were performed as an important component of the risk assessment to inform development of the guidance document. Simulated risk management strategies were examined with the purpose of reducing the prevalence of contaminated eggs and the number of illnesses per contaminated egg. The following observations were noted: Full vaccination of all laying flocks would reduce the number of illnesses to 4% of baseline (no vaccination) levels. Targeted vaccination (in other words, when the previously housed flock tested positive) would result in approximately the same reductions. A test and divert flock management strategy in which all laying flocks environments were tested for the presence of S. Enteritidis at the beginning of the laying cycle and 8-10 weeks before the end of lay, with diversion of eggs from flocks found to be occupying positive Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 8

9 environments, would reduce the number of illnesses to between 2% and 29% of baseline levels, depending upon whether the majority of infections occurred prior to the laying cycle or during the laying cycle, respectively. Replacing all pooled eggs in FSI settings with pasteurized egg products would decrease the number of illnesses to 29% of baseline (no substitution with pasteurized products). A 50% reduction in the consumption of raw or lightly cooked egg meals or recipes would decrease illnesses to 92% (FSI settings) and 72% (home settings) of baseline. Improving egg storage and handling conditions such that yolk membrane breakdown and growth of S. Enteritidis never occurred, would decrease the number of illnesses to 24% (FSI settings) and 56% (home settings) of baseline. 8. Guidance to Improve the Microbiological Quality of Shell Eggs Health Canada s goal is to protect the health of Canadian consumers by reducing the prevalence of shell eggs internally contaminated with S. Enteritidis offered for sale on the table market and to reduce the number of illnesses resulting from an internally contaminated egg. This guidance document outlines Health Canada s position on the microbiological safety of shell eggs with regards to S. Enteritidis. Due to the vertical transmission of the organism by the transovarian route, control measures that will ensure the microbiological safety of shell eggs with respect to S. Enteritidis will be most effective if they were to occur along the entire supply chain of the egg industry, from the grandparent flocks through to the time the egg is offered for sale to the consumer. Current flock prevalence data from the regulated laying flocks indicates that the prevalence of S. Enteritidis among regulated laying flocks is low, suggesting that current control programs should be continued. This has also influenced the types of simulated risk management options that were explored to improve current control programs. This guidance document also makes recommendations to address the risk of S. Enteritidis from other sources of grade A table eggs which may represent a source of increased risk to consumers. 8.1 Guidance for the Production of Table Eggs Reducing illnesses due to the consumption of eggs internally contaminated with S. Enteritidis can be accomplished by reducing the prevalence of contaminated eggs, and/or by reducing the number of illnesses per contaminated egg. Flock prevalence and contaminated egg prevalence within a positive flock have a direct effect on the number of illnesses from consumption of shell eggs, such that decreasing S. Enteritidis prevalence by a specified percentage results in an equivalent percentage decrease in the mean number of human illnesses (DeWinter et al., 2011). Preventing S. Enteritidis infection of laying flocks requires application of S. Enteritidis testing and/or control measures from the breeding flocks through to the laying flocks themselves. Timely sharing of data related to S. Enteritidis testing results between appropriate provincial and federal government and industry stakeholders is critical to the success of reducing S. Enteritidis in the industry. Testing programs have the added benefit of providing information as to the importance of various sources of S. Enteritidis infection, so that future HACCP-based control programs can be modified to adequately control for these sources. Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 9

10 8.1.1 Primary Breeders and Egg-Type Multiplier Breeders In any S. Enteritidis control program, it is internationally recognized that the most effective control can be applied using a top-down approach within the production scheme (Wray, Davies, and Evans, 1999). In Canada, the primary breeders are not considered to be a source of S. Enteritidis as these flocks are monitored for Salmonella every 3 weeks and are required to be SEfree. This also allows the primary breeders to meet the EU Export Protocol. The test results are shared with and monitored by the CFIA. Under an industry-led insurance program, the egg-type multiplier breeders are also required to be free of S. Enteritidis Production of day-old chicks Due to an industry-led program that comprises testing and control measures, the egg-type hatchery supply flocks (including the primary breeders and egg-type multiplier breeders) for the layer industry have rarely been identified as a source of S. Enteritidis over the past 15 years (Boucher, 2008; Cereno, 2012). However, this is not the case for the broiler sector and this source of S. Enteritidis could result in cross-contamination at hatcheries producing both egg-type and meat-type chicks, as well as at other stages where broiler operations may overlap egg operations (for example, common equipment or catching crews). It has been brought to Health Canada s attention that an investigation of human illnesses and outbreaks of S. Enteritidis from eggs pointed to regulated laying flocks that were infected with S. Enteritidis due to the numerous overlaps with the broiler sector. The CFIA currently performs fluff testing every six weeks in hatcheries for the detection of salmonellae. Day-old chicks are highly susceptible to S. Enteritidis infection; it follows that preventing exposure at this age is critical. Recommendation #1 Egg-type and meat-type chicken hatchery supply flocks should be free of S. Enteritidis. Hatcheries should source hatching eggs only from hatchery supply flocks that are free of S. Enteritidis. Layer hatchery supply flocks are already close to meeting this recommendation. Broiler hatchery supply flocks may need more time to work towards this recommendation. Recommendation #2 Egg-type chicks should not be raised to be or supplied as egg layers, where likely exposure to S. Enteritidis has taken place. Current protocols require notification of positive fluff test results to the industry stakeholder and the appropriate provincial egg board, who then decides upon the course of action. In addition, the CFIA should perform additional testing at the hatchery and the hatchery supply flock level to determine the source of S. Enteritidis. Exposure of egg-type chicks to S. Enteritidis should be Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 10

11 assessed using bacteriological monitoring programs, together with consideration of the protocols in use at the hatchery Pullet rearing Recommendation #3 Pullets should be reared using appropriate farm management and biosecurity practices to achieve sufficient separation from broiler operations as well as other poultry and other livestock operations, so as to prevent cross-contamination. Producers should consult with the appropriate provincial or federal government recommendations (for example, CFIA, Ontario Ministry of Agriculture, Food, and Rural Affairs) for additional information regarding poultry biosecurity, which should also provide a sufficiently separated environment for pullet production. Measures for rearing S. Enteritidis-free pullets will likely be found to be similar to the HACCPbased control measures for laying flocks, such as providing feed and water free of S. Enteritidis, rodent control, all-in all-out flock management practices, as well as effective cleaning and disinfection between flocks and effective biosecurity S. Enteritidis testing in pullet and laying flocks Recommendation #4 Pullets should be tested for S. Enteritidis at least once during the pullet-rearing stage. Laying flocks that are supplying shell eggs for the table market should be tested for S. Enteritidis a minimum of twice per laying cycle. Chickens can be infected through horizontal or vertical transmission, so testing should be practiced in order to detect both sources of infection. Test results should be provided to the CFIA to enable ongoing monitoring of trends related to S. Enteritidis, which will allow appropriate and effective use of program resources. Testing can also provide verification of the efficacy of On-Farm Food Safety programs in reducing the prevalence of Salmonella in laying flocks. Laying flocks should be tested for S. Enteritidis by performing environmental sampling, which is in line with current practices among regulated flocks and the scientific literature (Davies and Breslin, 2001; EFSA, 2010; Kinde et al., 2005). Currently, flock testing schemes are in place in all provinces, as specified by the provincial government or the provincial egg board, but many aspects of the sampling and methodology differ. The minimum standard appears to be that flocks are tested once during the laying cycle, approximately 8 to 10 weeks before the end of the laying cycle. Although the timing of this test provides information about the environment that the subsequent flock will occupy, it does not provide risk mitigation for the initial 42 to 44 weeks of egg production by that flock. Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 11

12 Pullets Testing should ensure that pullets are free of S. Enteritidis infection before transport to laying facilities. Due to the increased susceptibility of young birds, pullet testing should be performed early during the pullet growing stage to ensure that pullets being raised are not infected. The test results should be received in time to ensure that pullets are free of S. Enteritidis prior to shipment to a laying facility, and documentation of the results of testing can be provided to (and may be required by) the egg producer. Laying flocks In 1989, Humphrey demonstrated that naturally S. Enteritidis-infected laying hens tended to produce contaminated eggs intermittently, but at the same time by different hens in a flock. Since that study, other researchers have demonstrated that salmonellae are more likely to be isolated from infected birds or their environments during a period of stress (Holt, 1993; Nakamura et al., 1994). It is therefore thought that the increased production of contaminated eggs correlates with the degree of cecal carriage and increased fecal shedding (Davies and Breslin, 2001). Similarly, subclinical infections in hens may be exacerbated during periods of stress, resulting in increased shedding and an increased ability to detect S. Enteritidis in the environment. Therefore, testing at known times of stress would be expected to be more efficient at detecting infected flocks. Known sources of stress (not all of which are relevant to Canadian egg production) include induced molt, withdrawal of feed and water, temperature (too hot or too cold), introduction of new birds to a flock, handling and/or fright, disease and peak of lay. The Risk Assessment of Canadian Grade A Shell Eggs Internally Contaminated with Salmonella Enteritidis demonstrated that the number of illnesses due to S. Enteritidis in shell eggs would be expected to decrease as the number of times a flock is tested increases, and as environmental test sensitivity increases (DeWinter et al., 2011). Depending upon the relative importance of vertical and horizontal transmission of S. Enteritidis, two tests during the approximately 52 week laying cycle of all regulated flocks, plus diversion of eggs to further processing, would be expected to achieve a 71 to 98% reduction in contaminated egg prevalence. The recommended minimum testing for laying flocks comprises two tests, with the first test occurring between receipt at the laying facility and the peak of lay (between approximately 19 and 26 weeks of age). This is a period of time when the birds are physiologically stressed, and testing will effectively detect infected flocks. The timing of this test will also mitigate the risk of contaminated eggs produced from flocks infected early in the laying cycle. The second test should occur when the laying flock is between 36 and 60 weeks of age. Testing protocols in use as of (used in the risk assessment) dictate a minimum of one test, which generally occurred 8-10 weeks before the end of lay (corresponding to a flock age of 62 to 64 weeks of age). Testing 8-10 weeks before the end of lay has the advantage of increased test efficacy due to increased physiological stress of the laying flock as they approach the end of lay, and confidence that the subsequent flock is being placed into a clean environment. However, it also has the disadvantage that the receipt of test results usually occurs after the end of the laying cycle, thereby not permitting the diversion of eggs away from the table market. For this reason, it will also be acceptable for the second test to occur earlier in the laying cycle (when the flock is between 46 and 64 weeks of age) because this has the advantage of permitting the diversion of eggs from positive flocks, although there may be an associated decrease in test efficacy since the flocks are not likely to be experiencing stress at this time. The recommendations for the timing of testing allow 18 weeks of flexibility in the timing of the second test, but also incorporate a minimum of 20 weeks between the two tests so that the tests are fairly well-distributed over the 52 week laying cycle. Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 12

13 Recommendation #5 The practice of induced molting of laying flocks by feed withdrawal should be discontinued. Any molted laying flocks should undergo increased testing for S. Enteritidis. Although molting is rarely practiced in Canada, flocks that are molted experience increased stress. Molting induced by feed withdrawal has been associated with an increased rate of infection with salmonellae (Garber et al., 2003; Holt, 2003; Castellan et al., 2004; Gast, 2007; Golden et al., 2008). The increased S. Enteritidis prevalence among these flocks may also be associated with increasing environmental contamination in continuously occupied houses (Wales et al., 2007). Post-molt laying flocks should be tested every 3 months, with the first test for the post-molt flock occurring before the flock begins its next lay cycle. The literature is not conclusive as to whether induced molting using alternative methods results in an increased rate of infection with Salmonella (Callaway et al., 2009; Donalson et al., 2008; Gutierrez et al., 2008; Murase et al., 2006). Recommendation #6 For laying flock environmental testing for S. Enteritidis, all provinces and territories should follow at least the minimum national standard sampling protocol and methodology. Sampling in the flock environment should comprise a variety of samples. Currently, egg producers with regulated laying flocks supplying eggs for the table egg market must perform environmental testing for S. Enteritidis (EFC, 2012). The minimum microbiological sampling protocol for environmental testing specifies the following: Mandatory S. Enteritidis environmental testing of laying flock at least twice during the laying cycle; sampling carried out by qualified staff of the provincial or territorial egg board; 60 sites sampled per flock; focus on sampling dust and egg conveyances (swabs, dust, fluff, scrapings); additional sampling of rodent droppings and dead insects, if found; a minimum of 4 composited samples should be tested (that is, the samples from up to 15 separate sites may be composited); and the testing must be performed by an accredited laboratory using a cultural method for the isolation of Salmonella spp. approved by the Chief Veterinary Officer of each province. Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 13

14 The use of a minimum sampling protocol and methodology helps to ensure consistency in consumer safety and makes data comparisons possible. The determination of which sampling protocols and methodologies will form the basis of the testing program should be based on best practices, determined by a working group comprised of appropriate stakeholders including EFC, provincial egg boards, poultry veterinarian experts, the CFIA, and Health Canada. Sampling in the flock environment should comprise a variety of samples, such as dust samples from sources near the birds or from ventilation fans, egg belts, egg conveyances, egg spillage from conveyances, and/or the nest floor for nest systems, feces, manure, or litter, as well as vectors such as flies and rodents or their droppings. Dust samples should be emphasized in the sampling plan as they have been shown to be an important reservoir of Salmonella spp. (Kinde et al., 2005; Wales et al, 2006; Gast, 2007). Samples from agricultural environments are expected to have a higher load of background microbiota, including other Salmonella serovars. Therefore, a cultural method that permits sufficient resuscitation and has sufficient selectivity must be used for isolation. Methods intended for food and food manufacturing environments should not be used without sufficient validation Actions to be taken upon finding S. Enteritidis-positive flocks Recommendation #7 When the environment of a laying flock tests positive for S. Enteritidis, the eggs from that flock should be diverted for further processing, for the lifetime of that flock. After depopulation, cleaning and disinfection, the environment should be retested and not contain any salmonellae prior to repopulation with the subsequent flock. Furthermore, an investigation should be pursued by the provincial egg board or EFC to review biosecurity measures and suggest on-farm improvements as corrective actions. Where investigations are performed, the data collected regarding the potential sources of S. Enteritidis contamination can be used to improve the On-Farm Food Safety program. Recommendation #8 Pullet flocks that test positive for S. Enteritidis should not be supplied to egg producers for use as laying hens On-Farm Food Safety program recommendations Recommendation #9 Laying flocks that are supplying shell eggs for the table market should participate in a HACCP-based On-Farm Food Safety program designed to reduce S. Enteritidis, Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 14

15 and to address multiple potential sources of S. Enteritidis. On-Farm Food Safety programs for the egg industry should be reviewed periodically to ensure that all possible sources of S. Enteritidis are accounted for as new information and data become available. Specific attention should be given to the following: Poultry feed Sources of possible cross-contamination such as equipment, personnel and vectors Biosecurity practices between different operations (for example, layer or pullet flocks and broiler flocks on the same or different premises) Internationally, Salmonella has been recognized as a hazard in animal feed, potentially serving as an important vector for the introduction to a farm (Crump et al., 2002; EFSA 2008; Davies and Wales, 2010). In a Canadian study, S. Enteritidis was found in 2% (2 of 111) of finished pelleted poultry feed samples (Bucher et al., 2007), suggesting that feed may represent a source of exposure. Producers may wish to select feed for laying hens, pullets, and egg-type chicks that has undergone a treatment (for example, heat treatment) that has been verified to inactivate S. Enteritidis. Egg producers mixing feed on-farm should have their feed and/or feed ingredients tested regularly for S. Enteritidis Vaccination programs Recommendation #10 Laying flocks that are moving into houses that tested positive for S. Enteritidis while being inhabited by the previous laying flock, should be vaccinated. The relative prevalence of S. Enteritidis in vaccinated versus unvaccinated flocks has not been reported, but based on a 2004 study by Davies and Breslin, the average prevalence of positive eggs from positive non-vaccinated flocks is 25 times that in S. Enteritidis-positive vaccinated flocks. Vaccination of all regulated laying flocks was simulated to reduce contaminated egg prevalence by 96% in a risk assessment that evaluated the simulated effects of several risk management options on the prevalence of S. Enteritidis-contaminated eggs (DeWinter et al., 2011). Veterinary vaccines are licensed by the Canadian Centre for Veterinary Biologics of the CFIA. To meet the licensing requirements, each product must be shown to be pure, potent, safe, and effective when used as recommended in the target species according to the label claim. To conform to these requirements, salmonellosis vaccines are tested in vaccination-challenge experiments where groups of vaccinated birds and unvaccinated controls are exposed to S. Enteritidis, and monitored for evidence of infection and contamination of organs, tissues, faeces and eggs. Supplemental field efficacy studies may also be conducted to evaluate the benefits of vaccinating birds on S. Enteritidis-infected premises. The list of currently licensed veterinary vaccines for S. Enteritidis can be accessed on the CFIA s website (CFIA, 2012). Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 15

16 Vaccination should never be used as a substitute for cleaning and disinfection between flocks. Gast (2007) reported that neither inactivated nor live attenuated Salmonella vaccines have consistently prevented infection in layers, especially against high dose challenges. Vaccinating an incoming flock decreases the likelihood of a flock becoming infected, and has also been shown to decrease the rate of production of contaminated eggs, should a flock become infected. A vaccinated flock would still be subject to S. Enteritidis testing (as per 8.1.4), and the same actions would be taken in the event of a positive result. As an alternative to vaccination, the use of probiotics as a means of reducing Salmonella spp. infections may be considered in the future. Probiotics administered to chicks might prevent or decrease colonization of laying hens by S. Enteritidis, by extension resulting in a decrease in contaminated egg prevalence. However, a prerequisite for this would be the approval of probiotic products for such usage, by the Veterinary Drugs Directorate of Health Canada. 8.2 Guidance when Eggs are Implicated in Human Illness The Public Health Agency of Canada uses a variety of tools, such as the National Enteric Disease Surveillance Program and PulseNet Canada, to perform surveillance and investigate clusters or outbreaks of human illnesses. When eggs are implicated in S. Enteritidis illness and confirmed either epidemiologically or by isolation of the organism from the implicated food, a follow-up investigation is normally undertaken by the CFIA to determine the source of the eggs. When the originating flock is identified, it should undergo bacteriological examination for S. Enteritidis. Eggs from a positive flock or epidemiologically linked to salmonellosis should not be allowed for sale as table eggs, but should be sent to a processed egg station for further processing (see 8.3.8). If eggs from a positive flock are being sold at retail, a health risk assessment should be requested from Health Canada to determine the health risk level and any subsequent intervention measures to address the risk. 8.3 Post-Production Guidance for Table Eggs Additional recommendations for the safe production of eggs encompass a variety of issues related to the origin of the table eggs or to the handling of eggs from the point of lay through to the point of sale. These recommendations do not stem directly from the risk assessment. Any egg producer, regardless of size, may put consumers at risk by supplying eggs for the table market from a flock infected with S. Enteritidis (whether knowingly or not). In addition, eggs that are not stored or handled in a way that minimizes the S. Enteritidis hazard may put consumers at risk. The following two outbreak investigations provide evidence supporting the hypothesis that table eggs originating from sources outside the regulated sector may represent an increased public health risk. Taylor and colleagues (2012) investigated an increase in the rate of human infections with S. Enteritidis in British Columbia between 2007 and 2010 and identified eggs as the most likely source of illness; eggs were consumed both inside and outside the home, and the majority of the clusters were associated with the use of ungraded eggs in foodservice establishments. In Alberta in late 2010, there was an outbreak of S. Enteritidis involving at least 91 known cases that resulted in guilty pleas for 15 charges filed under the Public Health Act in the Alberta provincial court against a foodservice establishment (Slade, 2012). The outbreak was linked to the repeated sale of ungraded and dirty eggs to a foodservice establishment, with poor food Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 16

17 handling practices and a lack of refrigeration of the eggs cited as additional contributing factors (Everett, 2012). During the investigation, it was revealed that the sale of dirty ungraded eggs by the same individual had resulted in a first conviction in September 2002, with multiple subsequent convictions and fines leading up to the outbreak of The individual has been jailed twice for contempt of court for refusing to stop selling filthy, low-grade eggs on Calgary street corners despite repeatedly being ordered to stop (Cormier, 2012). In other provinces and territories, the source and quality of eggs is not captured during public health investigations, and therefore, it would not be possible to identify factors that contributed to illness when eggs are linked to human S. Enteritidis illnesses. This would be especially true in those provinces and territories that also permit the sales of cracked and/or ungraded eggs to consumers. The goal is to achieve a high level of consumer safety by recommending measures to equalize the microbiological risks associated with different sources of eggs Imported shell eggs destined for the table market Recommendation #11 Imported shell eggs should only be sourced from foreign exporters who can certify that eggs originate from laying hens under an equivalent testing scheme for S. Enteritidis, with environmental test results consistently being negative for S. Enteritidis. Imported shell eggs for the table market should meet the same requirements as Canadian table eggs. The aim is to ensure an equivalent level of protection for both domestic and imported products. Recommendation #12 The importation process for shell eggs (for both global and supplemental import permits) should allow effective traceforward and traceback investigations. It is anticipated that the implementation of the recommendations in this guidance document will result in standardized requirements for domestic table eggs in Canada, which will in turn permit a harmonization of requirements for table eggs that may also be applied to imported table eggs Surplus hatching eggs Recommendation #13 Surplus hatching eggs that are re-routed for human consumption should proceed to processed egg stations for pasteurization. Bureau of Microbial Hazards, Food Directorate, Health Products and Food Branch 17